Photo-flash lamp switching system



Dec. 10, 1957 R. E. GRIMM 2,816,251

PHOTO-FLASH LAMP swn cx-xmc SYSTEM Filed Oct. 21, 1954 INVENTOR M a fir %;Ys

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} PHOTO-FLASH LAMP SWITCHING SYSTEM Ralph E. Grimm, Washington, D. C.,, assignor, by mesne assignments, to Vitro Corporation of America, New York, N. Y., a corporation of Delaware Application october 21, 1954, Serial No. 463,727

2 Claims. (Cl. 315-231) This invention relates to a switching system for a photoflash lamp circuit.

Inphotograph work it is desired to have means for illuminating the work from either one or a plurality of photo-flash lamps, either singly or together, and with a variable wattage available for each lamp. The flash lamps are of the kind that are filled with an ionizable gas which upon being ionized by an induced voltage become conductive. The ionized gas'is then rendered incandescent by current received from one or more condensers in the circuit for each lamp.

Heretofore, a separate bank of condensers was necessary for each lamp, because if a single switch is used to connect two or more banks of condensers, with each bank having a capacity sufiicient to light the lamp, the currentv flow through the switch is great enough to burn the switch terminals. Consequently, it is difficult to synchronize the discharge of the separate condenser banks and the resulting light flashes. The inability of connecting separate condenser banks also made it impractical to use a plurality of banks to increase the power supplied to a single lamp.

The objects of the instant invention are to provide a switching system by means of which a plurality of separate condenser banks can be connected together or operated individually to supply various wattages to one or more photo-flash lamp sockets; to produce a system in which the condensers can be equally charged to equalize the power supplied to two or more flash lamp sockets; and to produce a switching system for connecting a plurality of condenser banks in which the switching terminals are prevented from being overloaded so as to cause arcing and burning thereof during the switching operatron.

In general these objects are accomplished by connecting the photo-flash lamp circuit sockets in parallel, the circuit for each flash lamp socket containing a bank of one or more condensers. These circuits are further connected in parallel by a plurality of resistances of progressively decreasing value selectively connected in by means of a single rotatable switch. The power supply is obtained from a single source connected to one of the flash lamp circuits, and led to another flash tube circuit successively through the plurality of resistances, which are such values that the current flowing through the switch is insuflicient at any time to cause arcing and burning of the switch terminals, while at the same time a means is provided for equalizing the charging of the condensers as the charging time lag between the various condensers due to the circuitry is compensated for, and for making various wattages are available at the individual flash lamp sockets.

The means by which the objects of the invention are obtained are described more fully with reference to the accompanying drawing, which shows a circuit diagram of the switching circuit constituting the invention.

to receive flash lamps of the type referred to heretofore.

z Socket A is connected through a switch 2 to a two-point make push button switch 4 which is further connected to a battery 6, or other source of high voltage supply. Similarly, socket B is connected through switch 8---t0- switch 4. It is clear that by actuating switches 2, 4 and- 8, sockets A and B may beindividually or simultaneously connected to a source of high voltage supply for thepufi pose of ionizing the gas in the flash lamps mounted in sockets A and B.

Socket A is connected to a power supply through li'ne 10, and to ground 12. Line 10 contains the bank of'condensers 14 and 16 in series. A source of power supply 18 is connected through line 20 and diode 22 to line 10 adjacent socket A, and connected through line 24 to-line 10 between condensers 14 and 16, and through line 26 containing resistor 28 to line 30, joined to socket B. Socket B is further connected to ground 32. Line 30 contains condensers 34 and 36 in series, and is joined to ground 38. Lines 10 and 30 are further connected by line 40, and to line 20 through line 42 containing diode 44.

Between lines 10 and 30 is a rotary switch 46. This switch is joined to line 10 by line 48. Switch 46 is selectively connected to line 30 through a plurality of resistances of progressively decreasing values. For example, resistance 50 may have a value of 22 K, and resistance 52 may have a value of 5,009, and resistance 54 may have a value of 479. Finally, line 56 containing resistance 58 connects lines 10 and 30 in parallel, and is further connectable through line 60 to switch 46 to bypass resistance 58.

As shown, switch 46 is open, and a circuit is established from current source 18 through lines 20, 10, 56, 30, 26 and 24, to charge condensers 14 and 34. In alternate cycles, condensers 16 and 36 are chargeable through the circuit consisting of lines 26, 30, 40 and 42. This makes a source of energy, for example watt-seconds, available for either socket A or B.

In the photo-flash unit in which'this circuit is designed to be used, power source 18 is turned on only just before the unit is to be used. It is a low power source which immediately begins to charge condensers 14 and 16. The charging of condensers 34 and 36 is either prevented or materially retarded by resistors 28 and 58. Consequently, at this time 100 watt-seconds are available to socket A from condensers 14 and 16.

If switches 2 and 4 are closed, socket A will be energized, and only one lamp will be illuminated with 100 watt-seconds of energy.

Each socket can be supplied with 100 watt-seconds for the simultaneous lighting of two flash lamps in the following manner. Switch 46 is turned into contact with the line containing resistor 50 of relatively high value. This establishes an intermediate auxiliary circuit to permit more current to flow to the condensers without overloading the switch terminals. At the same time, due to the circuitry, the condensers in line 30 lag behind the condensers in line 10 in charging time, and the use of this intermediate step gives condensers 34 and 36 time in which to charge up to equality with condensers 14 and 16.

Furthermore, if at this time condensers 16 and 14 are charged, and condensers 34 and 36 discharged, resistor 50 prevents condensers 14 and 16 from'being discharged into condensers 34 and 36, and thus protects the switch terminals from being burned by a high current surge. Switch 46 is then turned into contact with the line containing resistor 52 of less value than resistor 50 to increase the rapidity of charging, but at a safe value. This permits the condensers to be charged to a value of 100 watt-seconds in each of the lines 10 and 30, respectively. Upon closing switches 2 and 8, then switch 4, two lamps will be lighted simultaneously. When this is done, resistor 52 prevents line 30 from feeding into line 10.

When switch 46 is turned into contact with the line containing resistor 54, an intermediate circuit is established to permit the condensers to be charged rather rapidly to 100 watt-seconds without overloading the switch terminals. On then turning the switch to contact line 60, the current flows through the switch and line 56, by-passing resistor 58, to connect the banks of condensers in lines 10 and 30 into a single bank, and thus make the full charge of 200 watt-seconds of the coupled condensers available for one of either of lines 10 or 30, respectively. Again the intermediate step using resistor 54 serves to compensate for the lag in charging condensers 34 and 36. Consequently, 200 watt-seconds are available for either socket A or B, depending on whether switch 2 or 8 is closed, to light one flash lamp.

In the above description of a typical circuit, resistors 28 and 53 are 0.47 M, the condensers are each 525 mf., 450 v., and the power source 18 is 350 v.

It is noted that it is not necessary to turn switch 46 slowly, but that it can be turned as rapidly as possible by hand without disturbing the effectiveness of the circuit.

In addition to the advantage of coupling the banks of condensers without damaging the switch, the described circuit produces two photo-light sources from one circuit, whereas heretofore a separate condenser bank circuit was necessary for each photo-flash lamp.

Having now described the means by which the objects of the invention are obtained, I claim:

1. A switching circuit for energizing one or more flash lamps comprising a first lamp h'ne having a first condenser bank therein, source means for charging the condenser bank in said first line, a second lamp line having a second condenser bank therein, switch means connected to said first line, a resistance line joining said lamp lines, and a plurality of resistors selectively connectable to said switch means and said second lamp line, said switch means being provided for (a) charging said first condenser bank only from said source means, (b) charging said second condenser bank from said first lamp line to the value of the first condenser bank, and (c) for bypassing said resistors and the resistance in said resistance line to couple said first and second condenser banks to a single flash lamp line. i

2. A swtiching circuit for energizing a pair of flash lamps comprising a pair of electric lines containing condenser banks and flash lamp sockets, means for charging the condenser banks in one of the lines, a first resistance line joining said electric lines in parallel and having a resistor for charging the condenser bank in the other electric line with a time lag behind said one electric line, a second resistance line having a lower resistance than said first resistance line joining the electric lines in parallel, switch means for closing the circuit connection in said second resistance line to speed the condenser charging in said other electric line, and high voltage switch means for discharging the condensers in either of said electric lines with the flow of current from either electric line to the other electric line being blockingly delayed by the first and second resistance lines during the discharge.

References Cited in the file of this patent UNITED STATES PATENTS 2,447,832 Abend Aug. 24, 1948 2,464,188 Spinke Mar. 8, 1949 2,516,209 Henninger July 25, 1950 2,628,331 Rockafellow Feb. 10, 1953 

